Mercury and madhatters:

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Mercury and madhatters Implications of dose
response
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Dosage and Effect
As indicated in the last lecture, the impact of
trace elements on human health depends on
dosage. But the manner in which the human body
acquires these elements can complicate the
understanding of effect. For example, does the
dose involve high concentration exposure over a
short period of time, or low concentration
exposure over long periods of time. How do these
effects differ ? The effects of short-term, high
concentration dosage are often readily apparent.
But effects of long-term, low concentration
dosage are sometimes obscure.
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Dosage and Effect
Also, effects of exposure to toxic elements can
vary within populations depending on the age and
health condition of individuals For example a
low dose of a particular element may have
profound effects on infants, children, and the
elderly whereas the same dose may be relatively
benign among adults. Also, certain people can be
predisposed to adverse reactions to certain
elements (e.g. a person predisposed to cancer is
more likely to contract cancer due to exposure to
carcinogenic substances than a person who is
not). But the general symptoms are relatively
consistent within population
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The case of mercury
Issues related to exposure to mercury illustrate
well the complexity of these factors. Mercury
occurs in a variety of forms, but is always toxic
in high concentrations.

• Elemental mercury (pure mercury)
• in liquid form, a shiny, silver-white, liquid
  metal that beads
• In vapour form, a clear, colourless gas
• Inorganic mercury compounds (mercury combined
  with chlorine, oxygen or sulphur)
• -occurs as crystals (e.g. cinnabar HgS)
• Organic mercury compounds (mercury combined with
  organic molecules)
• -e.g. methylmercury
• -concentrated in high amounts in large,
• carnivorous fish near top of food chain

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Sources of mercury
Mercury occurs in a surprising variety of stuff !
Natural sources of mercury (elemental form or as
mercury compounds) volcanoes, hot springs,
weathering products of of some minerals in
rocks. Elemental mercury associated with human
activity thermometers, electrical switches,
fluorescent lights, thermostats, barometers,
batteries, dental fillings. About 80 of
elemental mercury released into the atmosphere is
linked to fossil fuel combustion in power plants,
mining, smelting, and solid waste incineration.
Inorganic mercury compounds associated with
human activity pigments (such as tattoo dyes),
vaccines, medicines (as a preservative, for
example), skin bleaching creams, disinfectants or
antiseptics, paints and pesticides. Use of
mercury in paint phased out in 1991. Organic
mercury compounds most common is methylmercury
(produced by activities of microbes- but source
of mercury often human-related) . Taken up by
living things and concentrated up food chain.
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How does mercury affect human health ?
On a basic level, mercury causes a net loss of
nerve tissue (due to degeneration of nerve tissue
and prevention of normal nerve development gets
in the way of the way proteins bind). In turn,
nerve damage is reflected in abnormal functioning
of nerve-controlled processes (both physical and
mental). Kidney damage long term exposure can
lead to eventual kidney failure and death (due to
inability of kidneys to remove waste products).
Other effects possible effects on fertility,
birth defects, cancer- but less well documented
than above
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Minamata Disease
We have already looked at the consequences of
short-term exposure to high concentrations of
mercury. Remember, Minamata disease was found to
be linked to ingestion of mercury-contaminated
fish in Japan. Again, the symptoms of mercury
poisoning were acute (and long-lasting) due to
irreparable nerve damage (including intrauterine
victims)
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Madhatter Syndrome
The Mad hatter character in Lewis Carrolls
Alice in Wonderland (1865) is not as whimsical as
one might think
Most people associate the phrase mad as a
hatter Alice in Wonderland, but was in use well
before this work. For example, Thomas Chandler
Haliburton (writer from Nova Scotia) in The
Clockmaker (1836) wrote Father he larfed out
like anything I thought he would never stopand
sister Sall got right up and walked out of the
room, as mad as a hatter In this case, mad
appears to refer to anger. But the term was more
commonly used to indicate insanity.
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An interesting aside
Lewis Carroll (1832-1898), was, in real life, the
Oxford Mathematics Lecturer (1855-81), the
Reverend Charles Lutwidge Dodgson. His pseudonym
reflects the derivation of his Christian
names Lewis Ludovicus Lutwidge Carroll
Carolus Charles
Alices Adventures in Wonderland and later
Through the Looking Glass written for Alice
Liddell.
Alice Liddell (in 1859- age 7)
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AnyhooWhat do hats have to do with mercury ?
Felt hats (e.g. top hats) were all the rage in
the 1800s Early manufacturers used beaver fur,
which matted well in its natural state As beaver
fur was becoming scarce (and was very expensive),
hat manufacturers started making hats from
cheaper fibres, such as rabbit fur. These
cheaper fibres did not mat as well as beaver fur,
so were chemically treated to enhance matting
ability
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Hat-making, contd
The hair was shaved off the animal skin to make a
crude felt. The felt was then boiled in boiling
acid to harden the felt. For added matting, the
felt was brushed with a solution of mercurous
nitrate Process was called carroting-
referring to the tendency of the mercury compound
to colour the hat orange.
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Finishing processes included steaming and ironing
the hat to shape it. Workers in the hat factories
(hatters) working in poorly ventilated
workshops would breathe in the mercury compounds
and accumulate the metal in their bodies. The
disease that uniquely afflicted hatters became
known as mad hatters syndrome
Physical Symptoms trembling (hatters
shakes) lurching gait loosening of teeth lair
loss loss of co-ordination slurred
speech drooling
Mental Symptoms irritability loss of
memory depression anxiety inability to think
clearly hallucinations
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The problem that wont go away
The use of mercury compounds in hat-making was
phased out by the mid-1900s, but does this mean
everything is o.k. ? Not necessarily Sediments
in rivers near Danbury Connecticut, once the
hat-making capital of the world in the 1800s
(56 factories), have been found to contain 67,000
parts per billion mercury (compared to accepted
level of 20,000 ppb). While normally buried out
of sight, out of mind, storms and floods can
remobilize sediments and release mercury into
river water, and ultimately to Long Island Sound
where it can taken up by plankton and fish. So
while threat of mercury poisoning may be
insignificant on a day-to-day basis, it may be
higher on the long term.
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Is mercury poisoning a modern phenomenon ?
One might think that, with all this use of
mercury in modern times,that mercury poisoning is
limited to the modern day. But there are signs
that the toxicity of mercury has been appreciated
for some time. For example, In Roman times,
criminals were sentenced to work in cinnabar
mines (cinnabar was widely used as a pigment in
the ancient world) This was obviously a death
sentence. Interestingly, Pliny described the
symptoms of mercury poisoning in the first
century AD.
Cinnabar (HgS)
So much for learning from the past, huh ?
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Does mercury threaten the average person in low
doses ?
Problem is, unlike the previously examined cases
of mercury poisoning that were characterized by
acute symptoms, symptoms of low-level exposure to
mercury can be obscure. In many cases, mercury
is one of many elements in a persons environment
that may produce adverse symptoms (so difficult
to pinpoint the cause of symptoms) We are in the
earliest stages of understanding human response
of low dose exposure.
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Health problems commonly blamed on mercury (but
which have not yet been proven to be linked to
mercury)
Mercury Amalgam Fillings
Mercury binds effectively with silver and
gold Silver or gold powder are mixed with tin or
tin/copper alloy and mercury (the mercury allows
the mixture to be molded into the cavity over an
extended period of time). Amalgam hardens and
assumes a permanent shape. The resulting
amalgam supposedly has good chemical stability in
the mouth, adheres well to tooth enamel, and has
a high compressive strength But some dispute
about possible health effects.
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Health problems commonly blamed on mercury (but
which have not yet been proven to be linked to
mercury)
Mercury Amalgam Fillings

• Health problems claimed to be linked to the use
  of mercury amalgam fillings include
• emotional problems (depression, anxiety,
  irritability),
• neurological disorders (facial twitches, muscle
  spasms, epilepsy)
• - cardiovascular problems (rapid heart rate,
  chest pains),
• - arthritis,
• - allergies,
• - digestive problems (ulcers, regional ileitis)
• - immunologic disorders (e.g. leukemia,
  mononucleosis).
• Is this a straw man effect, or are low doses of
  mercury responsible ?
• Anyones guess right now- need long-term studies
  (so far, inconclusive)

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Health problems commonly blamed on mercury (but
which have not yet been proven to be linked to
mercury)
Mercury and Autism
There has also been much talk about the link
between mercury and autism Thimerosal, a
mercury-based preservative used in some vaccines,
is under fire for an apparent increase in the
incidence of autism among children after being
given the MMR vaccine (measles-mumps-rubella). Bu
t interestingly, a recent study in Denmark (the
first country to ban thimerosal in 1992)
indicated a continued increase in autism
diagnoses after the ban (consistent with the rest
of world) Due to mercury, or simply better
diagnosis of autism ? Again, this is still under
debate the added concern here is the level of
risk imposed by not immunizing children (so
arguments are very heated right now).
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END OF LECTURE